Selective signaling by electromagnetic waves.



No. 727,326. PATENTBD MAY 5, 1903.

R. A. FESSENDBN. SELECTIVE SIGNALING BY ELECTROMAGNETIC WAVES.

APPLIOATI'ON FILED AUG. 27. 1902. N0 MODEL 2 SHEETS-SHEET 1.

WITN ESSES m: uonms Pawns cu, PHDTO-LITHU, WASNIN sssss 0 a No. 727,326. PATENTED MAY 5, 1903. R. A. FESSENDEN.

SELECTIVE SIGNALING BY ELECTROMAGNETIC WAVES.

APPLICATION mum AUG. 21, 1902.

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Patented May 5, 1903.

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REGINALD A. FESSENDEN, OF MANTEO, NORTH CAROLINA.

SELECTlVE SIGNALING BY ELECTROMAGNETIC WAVES.

SPECIFICATION forming part ofv Letters Patent No. 727,326, dated May 5, 1903.

Application filed August 27, 1902. Serial No. 121,173. (No model- To all whom it ntay concern:

Be it known that I, REGINALD A. FEssEN- DEN, a citizen of the United States, residing at Manteo, in the county of Dare and State of North Carolina, have invented or discovered a certain new and useful Improvement in Selective Signaling by Electromagnetic Waves, of which improvement the following is aspecification.

The invention described herein relates to methods of selective multiple and multiplex signaling by electromagnetic waves in which groups of electromagnetic waves of one kind are generated at the sending-station, the number of groups of electromagnetic waves per second being controlled by one or more controllers, each controller consisting of two or more mechanisms each adapted to cause groups of waves to be emitted at a predetermined rate per second, one emission rate be ing proper to each mechanism, While at the receiving-station I employ conductors tuned to the periodicity of the electromagnetic waves generated at the sending-station, and one or more receivers, each consisting of two or more mechanisms in operative relation to the conductor and arranged to produce a signal by conjoint action and each mechanism adapted to respond to one only of the emission rates of the sending end.

In the accompanying drawings, forming a part of this specification, Figure 1 is a dia-" grammatic view illustrative of my invention.

Fig. 2 is a similar view-illustrating a modification of the apparatus at the receiving-sta-" tion, and Fig. 3 is a diagrammatic View i1lus-;

trating a form of apparatus for multiple sending and receiving.

In the practice of my invention the radiating-conductor l is connected to one of the sparking-terminals 2, the other terminal be-,- ing connected to ground. While any suitable form or construction of generator, such as an induction-coil or a dynamo or dynamo and" transformer, as described in my previous patents, may be employed, for convenience the invention is illustrated and described in connection with an induction-coil and batteries. As shown, the terminals'of the secondary of the induction-coil 3 are connected, respectively, to the sparking-terminals 2. The primary of the coil forms part of a circuit containing battery 4 and two or more make-andbreak mechanisms A and B, independently operated at predetermined but different rates of speed by any suitable means. A convenient form of makeand-brcak mechanism consists of a cup 5, containing mercury, and a pin 6, movable into and out of the mercury. A suitable means for shifting the pin consists of a small electric motor 7, having the pin so connected to its armatu re-shaft as to be moved up and down during the rotation thereof.

The rotation of the motor may be controlled in any convenient manner, as by the tuningfork 8, which is electrically driven and controls bya coil on the armature-shaft of the motor the rotation of said shaft, said coil being included in the circuit with the tuningfork, this method of control being well known in the art. If the tuning-fork of the makeand-break mechanism A is adjusted to a certa'in number of periodssay two hundred and fifty-six (256) per second-the motor will 'be so operated as to break the primary cirperiod. It is preferable that the height of mercury in the cup should be such (relative to the length of stroke of the pin) that the duration of contact should be several times the duration of break. A sending-key 9 or any suitable form of make-andbreak mechanism is included in the primary circuit. The sending-conductor is proportioned and arranged so as to radiate waves of any desired singlefrequencyg.,'two million per second.

-At the receiving-station the conductor 10 has a wave-responsive device, as the loop 11, arranged in operative relation thereto, said Wave-responsive device being also included in a circuit containing two or more electromagnetic mechanisms adapted to'operate in unison respectively with the periods of the make-and-break mechanisms at the sendingstation. The loop 11 is preferably constructed as described and shown in Letters Patent No. 706,744, granted to me August 12, 1902. A convenient construction of electromagnetic mechanism consists of a telephone 12, having two or more tongues 13, forming parts of microphonic contacts included in circuits which also include the coils of a telephone 14, having two or more poles. The make-and-break mechanisms A and B are preferably adjusted to operate at such rates as to produce notes which when combined will form a chord, and as the tongues of the telephone12 are adjusted to respond only to groups of waves emitted at such rates achord will not be produced by telephone 14 by groups of waves emitted at different rates.

In lieu of the construction shown in Fig. 1 the receiving apparatus shown in Fig. 2 may be used. As therein shown, the circuits having the microphonic contacts 13 also include controlling devices (such as the loops 15) which control the currents in the circuits of the double movable coil-relay having permanent magnets 16. Contact-fingers 17 on the movable coils 18 of the relay are connected in the circuit including an indicating mech anism 19, said circuit being closed only when both fingers are brought simultaneously against the contact-plate 20. Condensers 21 are included in each microphonic circuit to cut out steady currents; but the circuits are not electrically tuned, as such tuning is not necessary.

The method of operation is as follows: The make-and-break mechanisms A and B being operated at predetermined but different rates, the key 9 is depressed for a sufficient length of time to form a dot or dash of the Morse code. During this period the make-and-break mechanisms cause groups of electromagnetic waves of the same character and periodicity (2'. e., two million per second) to be emitted; but one set of groups of waves has an emission rate of, say,two hundred and fifty-six per second and the other set of groups of waves an emission rate of, say, three hundred and eighty-four per second. These groups -of waves acting on the receiving-conductor .and receiving mechanism cause the tongues 13 of the electromagnetic mechanism to respond,said tongues being mechanically tuned to vibrate, respectively, at the rates corresponding to the rates of the make-and-break mechanisms A and B. These tongues actuate the microphonic circuits which actuate the coils of the relay 16 to close the indicatingcircuit andproduce a dot or a dash. Where the loop 15 is usedto operate the double relay, (shown in Fig. 2,) the vibration of the microphonic contacts or tongues 13 generate a fluctuating or alternating current in the circuit 13 15, which fluctuating current heats up the loop 15, thereby changing the resistance in the local circuit 18 15, and thus changing the position of the coil 18 of the double relay to complete or close the contacts at 20, which contacts control the indicating-circuit.

Since only one character of electromagnetic waves is generated and the receiving-conductor is tuned to respond only to waves or" that character and since in addition the electromagnetic receiving mechanisms are mechanically tuned to respond only to the wave-emission rates at the sending end and since also the conjoint action of the receiving mechanisms is also necessary to produce an indication, it will be seen that the system is strongly selective.

My improvement may also be used for multiple working, as by using a plurality of tongues 13 on the electromagnetic mechanism 12, as shown in Fig. 3, and grouping themin sets, each set controlling a bipolar telephone or a double movable coil-relay, two or more messages may be received at the same time, each set of tongues being mechanically tuned to different stations. It will be readily understood that each pair of make-and-break mechanisms A and B when operated by the key 9 may be used to send a message independently of every other pair, just as it each pair were alone operating a station. Similarly, at the receiving-station the tongues 13 of one telephone 12 may be tuned to correspond to one pair of make-and-break mechanisms A and B and receive the message sent by said pair, while a second pair of tongues may be tuned to a second pair of make-andbreak mechanisms A and B, so as to receive the message sent by such pair. Similarly, by using a plurality of make-and-break mechanisms at the sending-station and grouping them in sets, each set being capable of actuating the coil, as by operating one primary of an induction-coil having several primaries and having a secondary common to all the primaries, several messages may be sent simultaneously, because although both pairs of make-and-break mechanisms produce an effect on a wave-responsive device 11 the first .pair of tongues will only be affected by the first set of make-and-break mechanisms, since the tongues are tuned to the first pair only and will not respond conjointly to any other pair of make-and-break mechanisms. Similarly, asecond pair of tongues will only respond conjointly to a second pair of makeand-break mechanisms.

This system may also be used for multiplex work, for by placing a receiving mechanism, (indicated at 21 in Fig. 3,) said mechanism being of any suitable form, such as that shown :in Fig. 2, in the secondary of a transformer part of whose primary is formed of turns in the vertical wire 1 and part formed of turns in the parallel tuned circuit 22, which operates as described in Patent No. 706,735, granted to me August 12, 1902, the primary turns may be wound in such a manner that when sending (and hence in parallel) they oppose IIO and neutralize each others effect on the secondary, and hence do not affect the receiving mechanism, but when receiving act in series to aid each other. As shown, the local circuit is unsymmetrically arranged with reference to the spark-gap or point at which the local circuit acts upon the vertical-2'. 6., the center of oscillation of the electrical charge in the local circuitis displaced to onesideofthespark-gap. This displacement is preferable, because the spark-gap in the vertical being at a certain height above the ground, and hence at a certain distance to one side of the center of oscillation of the electrical charge in the vertical wire, the charges in the local circuit and in the local wire will not'oscillate in harmony through the entire period unless both circuits are displaced an equal fraction from the center of oscillation at the point where they intersect, and hence will not produce sharp resonant effects. In such an arrangement no effect (or a proportionately much smaller effect) will be produced on the receiving mechanism by sending from its own station, while the receiving mechanism remains free to be affected by outside signals. Hence it is possible to send from and receive simultaneously at the same station. Hence two different messages may be sent simultaneously to two different stations or to same station, one being sent by each pair of make-and-break mechanisms A and 13, while at the same time messages from another station may be received by the receiving device 21. stood that more than one pair of tuned tongues and devices controlled thereby may be employed to receive a corresponding number of messages.

Where multiple working is used,'or generally in any case where heavy currents are received, it is preferred to employ two or more loops in parallel, as shown in Fi 4, or other equivalent means-e. g., a single loop of larger cross-section, which may be conveniently formed by ruling a line'with an insulating-varnish about one one-hundredth of an inch wide on a thin platinum or other metallic foil, plating the non-insulated surface of the foil to any desired thickness, dissolving off the insulation, and cutting the foil into slips of the desired width.

I claim herein as my invention 1. In a system of signaling by electromagnetic waves, radiating and receiving systems having one or more elements in common and a receiver so related to said systems as to be responsive to electromagnetic waves received at the station, while at the same time unresponsive to effects produced by the generation of electromagnetic waves at the station.

2. In a system of signaling by electromagnetic waves, radiating and receiving systems having one or more elements in common and a receiver so related to said systems as to be more sensitive to electromagnetic waves received at the station than to effects produced It will be underby the generation of electromagnetic waves of the same frequency at the station at the same time.

3. In a system of signaling by electromagnetic waves, the combination at a station of a receiver for electromagnetic waves, and means for generating electromagnetic waves, said elements being so connected as to perform their functions simultaneously without interference one with the other.

4. In a system of signaling by electromagnetic waves, the combination at a station of a generator of electromagnetic waves, two conductors, a receiver for electromagnetic waves, in operative relation to said conductors, said conductors being so connected as to oppose the effects on the receiver produced by the generation of electromagnetic waves at the station and to conjoin the effects on the receiver produced by electromagnetic waves received at the station.

5. In a system of signaling by electromagnetic waves, the combination at the receivingstation of a Wave-responsive device, a circuit containing a microphonic contact controlled thereby, a conductor adapted to be heated by currents in said circuit, and an indicating mechanism controlled by heat effects in said conductor.

6. In a system of signaling by electromagnetic waves, the combination at a station of two conductors and a receiver for electromagnetic waves in operative relation to said conductors, said conductors being adapted to oppose the effects on the receiver produced by transmitting electrical impulses, while permitting waves of the desired periodicity to affect the receivers.

7. In a system of signaling by electromagnetic waves, radiating and receiving systems and a receiver so connected to said systems as to be unresponsive to effects produced by the generation of electromagnetic waves at the same station as the receiver but responsive to electromagnetic waves received at the station, substantially as set forth.

8. In a system of signaling by electromagnetic waves, radiating and receiving systems and a receiver more sensitive to electromagnetic waves received at the station than to 'efiects produced by the generation of electro ICC ally placed with reference to the point of into teraction between the conductor and the auxiliary circuit, substantially as set forth.

In testimony whereof I have hereunto set my band.

REGINALD A. FESSENDEN. Witnesses: I GEO. B. BLEMING,

BAYARD H. OHRIsTY. 

